Vibrant Performance Spark Plug Boot Insulators protect your spark plug wires at the boot connection with an easy, slip on fit. These spark plug heat shields are constructed from braided fiberglass to give you protection up to 1200° (649° Celsius) and do not require any clearance from the heat source. With a 3/4" inside diameter these spark plug protectors should fit most common spark plugs. Sold in quantities of 4.